Explosive means



July 2, 1963 D. 1.. COURSEN 3,095,812

EXPLOSIVE MEANS Filed June 27, 1960 2 Sheets-Sheet 1 INVENTOR DAVID L.COURSEN ATTORNEY y 1963 D. 1.. COURSEN 3,095,812

EXPLOSIVE MEANS Filed June 27, 1960 2 Sheets-Sheet 2 INVENTOR DAVID L.COURSEN ATTORNEY 3,tl5,812 EXPLOSIVE MEAN David L. Coursen, Newark, Del,assignor to E. I. du Pont de Nernours and Company, Wilmington, Del., acorporation of Delaware Filed .Inne 27, 1960, Ser. No. 39,192 Claims.(Cl. 102--27) The present invention relates to explosive devices whichfunction as valves or'as relays for detonation. This application is acontinuation-in-part of my copending application Serial No. 683,049filed September 16, 1957, now abandoned.

In a number of applications, signaling or actuating means responsive toimpulse from one direction but not from another are widely used. Manyelectrical devices which function thus are known and used, for example,in computers. A need has existed for an equivalent explosive means whichcan act as a relay or selective valve.

Accordingly, an object of the present invention is to provide anexplosive device which will have directional selectivity. A furtherobject is to provide an explosive device which will transmit detonationimpulses only when such impulses reach the device from a predetermineddirection. Additional objects will become apparent as this invention ismore fully described.

I have found that an explosive device having directional selectivitycomprises a sheathed detonating explosive core in helical configurationand a sheathed detonating explosive core axially positioned within thehelix, the ratio by weight of the total explosive to the total sheathingfor the combination thus formed being within prescribed limits. Thedescribed device is the result of my discovery that when the ratio byweight of the explosive and the sheathing is within the prescribedlimits, the concentration of explosive energy produced by theprogressive detonation of the explosive core in the helicalconfiguration will produce initiation of detonation in the axialexplosive core but only in the direction of the axial component ofdetonation in the helix, i.e., the lateral direction in which thedetonation progresses in the helix, and further that a detonationtraveling through the axial explosive core will not initiate detonationin the surrounding helical core.

In order to more fully describe the present invention, reference is nowmade to the accompanying drawings in which:

FIGURE 1 represents a detailed view of two lengths of detonating cordassembled in accordance with this invention;

FIGURES 2 to 11 inclusive are schematic diagrams of explosive corearrangements in accordance with this invention; and

FIGURES 12 and 13 are schematic diagrams showing the use of the presentassemblies in blasting set-up.

Referring now to FIGURE 1 in greater detail, 1 represents a length ofdetonating cord having a portion thereof in the form of a helix 2. 3represents a second length of detonating cord passing through the helix2 in axial alignment therewith. 4 represents a sheath, for example ofmetal such as lead, and 5 represents a detonating explosive, for examplePETN, which forms the core of the cords 1 and 3. The constructiondescribed forms the basis for all of the arrangements shown in theremaining figures, in which, for simplicity of illustration, only thecore, as represented by a line, is shown.

Referring now to FIGURE 2, the following information can be given. Adetonation originating at A will continue on to B, and in passingthrough the helix Y, will pro- 3,95,8l2 Patented July 2, I963 duce noinitiation of column CD, but will destroy the helix Y. Similarly, adetonation originating at B will continue on to A and no initiation ofcolumn CD will occur, but helix Y will be destroyed. An initiationoriginating at C will continue through helix Y and on to D. The cord ABwill be initiated inside the helix Y in the direction of B only, i.e,detonation will go on to B but not to A. A detonation originating at Dwill go on to C, and will initiate a detonation towards A but nottowards B.

In the embodiment shown in FIGURES, a detonation originating at E willpass through the helm; Y and, if the loop is very small, will pass on toF by traversing the helix Y before it is sufiiciently destroyed to stopthe propagation of detonation. If the loop is larger, the helix will bedestroyed before the detonation can be transmitted through the explosivecore, and the detonation will cease. A detonation originating at F willalways cease in the loop because the core passing axially through thehelix is initiated in the direction of the loop and the core in thehelix is detonating toward the loop. When the two detonation fronts meeton the loop, propagation of detonation ceases.

The embodiment shown in FIGURE 4 is a variation of that of FIGURE 3. Thesize of the loop will again control whether detonation can go from E toF. However, in this embodiment, detonation originating at F will betransmitted to E by initiation of the core leading to E at the helix Y.

In the assembly shown in FIGURE 5, a detonation originating at either Gor H will pass to H or G respectively without initiating any other cordbut destroying helix Y and helix Z. A detonation originating at I willcause initiation of cord GH at helix Y in the direction of H only. Ifthe length of the cord 11 between helix Y and helix Z is of greaterlength than that of GH between the helices, the detonation will continueon to H but not to I. On the other hand, if the length of the cord IIbetwen helix Y and helix Z is less than that of GH between the helices,the detonation will go on to I, but not to H. If the lengths areapproximately the same, detonation will go on to both H and I. Adetonation originating at I will initiate a detonation on to H and, ashort interval later, a detonation on to G, and will continue on to J.

In the embodiment depicted in FIGURE 6, detonation originating at eitherM or N will pass on to N or M respectively without producing any otherinitiation but destroying helix Z. Detonation originating at L willproduce detonation toward K and toward M but none toward N. Detonationoriginating at K will cause detonation towards N only.

Referring now to the system shown in FIGURE 7, detonation Originating atQ will cease unless the loop is small enough so that it can continue onto R. Detonation originating at R will always cease. Detonationoriginating at 0 will go on to P and will initiate detouations to both Rand Q. Detonation originating at P will go on to Q and will initiatedetonation to Q only.

In the variation shown in FIGURE 8, detonation originating at Q is asfor Q in FIGURE 7. Detonation originating at R will initiate detonationto Q only. Detonation originating at 0 will go on to P but will initiatedetonation to R only. Detonation originating at P will go on to 0' butwill initiate detonation to Q only.

In the embodiment shown in FIGURE 9, detonation originating at S will goon to V, the detonation induced in cord TU towards T being interruptedby the destruction of helix Y. Similarly, detonation originating at Uwill go only to T. Detonation originating at T will go on to U and willinitiate detonation On to S only. Detonation originating at V will goonto S and will initiate detonation on to U only.

In the variations shown in FIGURE 10, detonation originating at S willgo on to V and will initiate detonation on to U only. Detonationoriginating at V will go on to S and will initiate detonation on to Tonly. Detonation originating at U will go on to T and will initiatedetonation on to S only. (Obviously, variations in the lengths of thetwo cords between helices will cause variations in the directions inwhich detonation will go. For example, if the length of TU betweenhelices is greater than that of SV', detonation originating at V willinitiate detonation toward T, but the prior detonation of the cord to Swill destroy helix Y so that the detonation toward T will be cut ofi.)

In the arrangement shown in FIGURE 11, detonation originating at S" willgo on to V", all other detonations failing. Detonation originating at Twill go on to U", all other detonations failing. Detonation originatingat U will go on to T and will initiate detonation towards S" only.Detonations originating at V will go on to S and initiate detonation toU" only.

Obviously the foregoing represent only a few of the multitude ofcombinations which can be produced, but serve to illustrate the manypossibilities inherent in this invention. The detonating cords can beused to actuate assemblies, the sequence or selection depending on thesource of the signal.

FIGURES 12 and 13 illustrate the application of the devices of thepresent invention to make blasting safer. In the figures, 6 representsan explosive charge in a borehole, 7 represents the surface of theearth, 8 represents a down-line of detonating cord, 9 represents asurface trunk line of detonating cord, 10 represents a one-waydetonating valve in accordance with this invention, 11 represents aconventional initiator, and 12 represents a stop-go device in accordancewith the present invention.

When trunk line 9 is initiated by detonation of initiator 11, thepassage of detonation through units 10 initiates the down-lines 8, thusinitiating charges 6. If one of charges 6 or down-line 8 is accidentallyinitiated, the detonation of down-line 8 in unit 10 will not initiate adetonation in the trunk line 9, thus eliminating the danger of theaccidental detonation of one charge causing the premature detonation ofother charges. When units 12 are inserted as shown in FIGURE 13, theadditional factor is introduced that only detonation from the directionin which the initiator 11 is located can be transmitted along the trunkline 9.

In order to more fully illustrate the present invention, reference isnow made to the following examples. In each case, the direction ofdetonation was determined either by means of impressions produced on alead block or by X-ray pictures taken during detonation.

EXAMPLE 1 A large number of units were prepared having the configurationshown in FIGURES 1 and 2. Both the helix and the central column wereprepared from a leadsheathed explosive core consisting of a mechanicalmixture of 98 parts of finely-divided PETN and 2 parts of Fe O Theexplosive mixture was present in the amount of 0.0042 gram percentimeter of length, and the lead sheath was present in the amount of0.0615 gram per centimeter of length evenly distributed about theexplosive core. Thus the sheath to explosive weight ratio in eachassembly formed was about 14.6 to 1.

In the following tests, the unit was initiated by means of an electricblasting cap positioned at the point labeled in FIGURE 2. The helix hadan inner diameter substantially equal to the outer diameter of thecentral column, so that no air gap existed between the helix and thecentral column, and the turns of the helix were adjacent to each other,so that no air gap existed between the turns.

Table I Number of Detonations Arriving at Number of Turns in Helix 1Number of Units B only D only B ml Other Figure 2 illustrates 2 turns.

When the foregoing tests were repeated under identical conditions exceptthat the turns of the helix were separated from each other byapproximately 0.10 centimeter, thus providing an average air gap of 0.10centimeter in all cases the detonation arrived at D only, i.e., thecentral column was not initiated.

In ten units in which the helix consisted of 2 turns with no air gap,and initiation was at point A rather than point C, detonation arrived atpoint B only.

EXAMPLE 2 In units identical to those described in Example 1 (turns ofhelix in contact with each other) except that the lead sheathing on thestraight column amounted to 0.452 grams per centimeter of length, thefollowing results were obtained when the unit was initiated at C. Ineach case the ratio of the sheath weight to explosive weight in theassembly was about 22 to 1.

Table II Number of Detonations Arriving at- Number of Turns in HelixNumber of Units B only D only B 125nd Other Detonation arrived at only Bwhen the unit was initiated at A.

EXAMPLE 3 A number of units having the configuration shown in FIGURE 3were prepared using a lead-sheathed explosive core consisting of the 98%-PETN-2% Pe -O mixture, the explosive loading corresponding to 0.0042grain per centimeter of length and the sheath corresponding to 0.0615gram per centimeter of length. In all dimensions, detonation initiatedat F stopped in the loop and did not propagate to E. When the loop had adiameter of less than 1.8 centimeters, and detonation was initiated atE, the detonation was propagated to F. When the loop had a diametergreater than 1.8 centimeters, detonation initiated at E was notpropagated to F.

The foregoing examples illustrate that, under proper conditions, a helixof a sheathed detonating explosive core having a sheathed detonatingexplosive core aligned axially within the helix produces a one-way valveor relay for detonations. The experimental evidence shows that forconsistent usefiul results, the helix must consist of more than one turnof the sheathed explosive core and that the turns must be essentially incontact with each other. The sheathing of the helical explosive coreshould be essentially in contact with the sheathing of the axialexplosive core.

As shown, the detonation traveling through the axial explosive core doesnot initiate a detonation of the explosive core in the helix, althoughthe helix is blown apart, and thus rendered non-functioning. Adetonation traveling through the explosive core forming the helix willinitiate detonation in the explosive core in the axial column, but onlyin the lateral direction of detonation of the explosive core of thehelix. If the helix has from 1 /2 to 2 /2 turns, the detonation willcontinue through the helix. If, however, the helix has 3 or more turns,the detonation will not continue through the helix but only in theexplosive core of the axial column. Presumably, this is due todestruction of the end portion of the helix by detonation of theexplosive core of the axial column so that further propagation ofdetonation through the helix is not possible.

In the examples, I have illustrated the use of a PETN explosive core ina lead sheath to form both the helix and the axial column. This form ofexplosive cord is particularly adaptable for use in preparing thedevices of the present invention because of the ease 'of handlingplosive core in the axial column should be from 5 to 50 times thecombined weight of explosive core in the combination thus formed. Underthese conditions, initiation of one core will not occur from detonationof the other core when they are simply adjacent to or cross over eachother, but will occur when the detonating core is in the form of ahelix.

Instead of the metal-sheathed explosive core I may use the conventionalfabric covered detonating iuse containing from 0.064 to 0.160 gram ofexplosive per centimeter of length, provided sufiicient additionalsheathing is applied to provide the required mass ratio between thesheathing and the explosive. Commercial 50 grain per foot Primacord(manufactured by the Ensign-Bick ford Co.), conventionally used inblasting operations, has an explosive loading of 0.106 gram of PETN percentimeter of length and a sheathing mass of 0.131 gram per centimeterof length. Thus the sheath to explosive wei ht ratio of an assemblyprepared from such cord would be only about 1.22 to l and thedirectional selectivity would not be obtained. This explains why knotscan be used to transmit detonation from one line to another in ordinaryblasting practice.

If desired, the devices of the present invention may be prepared in theform of a unitary package by potting the valve in cement or in asynthetic potting resin. Such procedure would be necessary only if roughhandling might otherwise disturb the configuraion of the valve.

The present invention has been described in detail in the foregoing.Many applications of the explosive valves will become apparent to thoseskilled in the art. Accordingly, I intend to be limited only by thefollowing claims.

I claim:

1. An explosive device having directional selectivity comprising incombination a length of a sheathed detonating explosive core in helicalconfiguration consisting of a plurality of turns and a second length ofa sheathed detonating explosive core axially positioned within saidhelical configuration, the said helical c'o'n figuration being such thatthe sheathing of each turn of said explosive core therein is in contactwith the sheathing of its adjacent turn and with the sheathing of thesaid axial core, the ratio of the weight of sheathing to explosive insaid explosive device being between 5 and to 1.

2. An explosive device as claimed in claim 1, wherein both lengths ofdetonating explosive cores consist of from 0.0021 to 0.021 gram percentimeter of length of a cap-sensitive detonating explosive within ametal sheath.

3. An explosive device as claimed in claim 1, wherein the explosive isPETN.

4. An explosive device as claimed in claim 2, wherein the metal sheathis lead.

5. An explosive device as claimed in claim 1, wherein the length ofsheathed detonating explosive core in helical configuration and thesecond length axially positioned within said helical configuration arejoined by a length of sheathed detonating explosive core which connectsan end of said length of core in helical configuration with an end ofsaid axially positioned core.

References Cited in the file of this patent UNITED STATES PATENTS882,154 Lheure Mar. 17, 1908 2,414,349 Alexander Jan. 14, 1947 2,535,518Rich Dec. 26, 1950 2,715,365 Godchaux Aug. 16, 1955 2,980,017 CastelApr. 18, 1961 OTHER REFERENCES Blasters Hand-book, page 152, publishedby Canadian Industries Ltd., Montreal, Quebec, Canada (1954). (Copy inDiv. 10.)

1. AN EXPLOSIVE DEVICE HAVING DIRECTIONAL SELECTIVELY COMPRISING INCOMBINATION A LENGTH OF A SHEATHED DETONATING EXPLOSIVE CORE IN HELICALCONFIGURATION CONSISTING OF A PLURALITY OF TURNS AND A SECOND LENGTH OFA SHEATHED DETONATING EXPLOSIVE CORE AXIALLY POSITIONED WITHIN SAIDHELICAL CONFIGURATION, THE SAID HELICAL CONFIGURATION BEING SUCH THATTHE SHEATHING OF EACH TURN OF SAID EXPLOSIVE CORE THEREIN IS IN CONTACTWITH THE SHEATHING OF ITS ADJACENT TURN AND WITH THE SHEATHING OF THESAID AXIAL CORE, THE RATIO OF THE WEIGHT OF SHEATHING TO EXPLOSIVE INSAID EXPLOSIVE DEVICE BEING BETWEEN 5 AND 50 TO 1.